Mixing apparatus



April 5, 1960 Filed Feb. 27, 1958 3 Sheets-Sheet 1 a! f/ (V '77/ a2 (1 65 1vENToRs' Aiik l: I? mmbel [mil fl. fiih/IM AGENT April 5, 1960 K,RUMBEL ETAL 2,931,633

MIXING APPARATUS Filed Feb. 27, 1958 3 Sheets-Sheet 3 INVENTORS AGENTUnited States Fatent 2,931,633 MIXING APPARATUS Keith E. Rumbel, FallsChurch, and Earl D. Hilburn, I

Alexandria, Va., assignors to Atlantic Research (Forporation,Alexandria, Va., a corporation of Virginia Application February '27,1958, Serial No. 717,95 1'6Claim's. or. 259- -104 This invention relatesto a laboratory mixer particularly designed to provide versatility inexperimental mix- I ing and for eificiency in mixing small batches.

One of the objects of the invention is to provide a mixer of the generaltype described including means providing controllable thermal andatmospheric environment for the mixing receptacle. Another object of theinvention is the provision of a laboratory mixer in which the mixingreceptacle is surrounded by a vacuum chamber thereby establishing abalanced sub-atmospheric pressure both inside and outside the mixingreceptacle, preventing air from being laboratory mixer in which themixer can be completely disassembled or reassembled in thelaboratorywithout tools or special skills' in a matter of seconds, permittingsimple and thorough cleaning, saving time between batches and avoidingbatch to batch contamination.

Other objects of the invention will appear as the description of apractical embodiment thereof proceeds, it

being understood that while the practical application of the inventionin immediate contemplation is its use as laboratory apparatus, the scopeof the invention is to be regarded as suflicientlycomprehensive toinclude the construction and use of larger units for the mixing ofbatches of production magnitude. 7

In the drawings which accompany and form a part of the followingspecification and throughout the figures of which the same referencecharacters have been employed to denote identical parts.

Figure 1 is a perspective view of.a power plant in which the mixer formsa component.

Figure 2 is a section in a vertical plane taken along the line 2-2 ofFigure l.-

Figure 3 is a'horizontal section taken along the line 3-3 of Figure 2. iFigure 4 is a fragmentary view in vertical section taken along the lineof Figure 2.

2,931,633 Patented Apr. 5, 1 960 2 motor 4, and gear box 5, the lattercontaining the gear assemblage by means of which the mixer is drivenfrom the motor. The motor and gear box are permanently fixed to thebase, but the mixer is slidably mounted upon tracks 6, which aresecuredto the base, so that it can be slidably moved into or out ofcoupled relation to the gear assembly. When in uncoupled position themixer 3 can be lifted bodily from the base, for the purpose of variousmanipulations, including tipping it for pouring out its contents.

Adverting now to the structural details of the mixer per se as shown, itcomprises. a pedestal 7 consisting of a fiat base plate 8, which in theexemplary form shown is of square dimensions, having rounded corners andformed with a large circular opening centrally located from thecircumference of which an integral cylindrical sidewall 9 extendsupwardly, said pedestal terminating in a flat top 10 integrally meetingthe upper circumferential edge of the wall 9. The base plate 8 projectsbeyond the circumference of the sidewall 9, forming a flange which isnarrowest at the points 11, at which points the sides of the base platecomes closest to be tangent to the circumference of the sidewall. Thetop 10 is parallel to the base plate. Said base plate on its underface,at opposite sides, is formed with the channels 12 which interfit withthe tracks 6.

The mixing receptacle 13 is made with a lower body member 14and an upperbody member 15. These, to

gether, are formed at their opposite sides with cylindrical bearingseats 16, and the horizontal plane of separation between the twobodymembers passes through the axes of said seats. The lower body member14 begins with an annular base flange 17 which rests upon the topwall 10of the pedestal, an annular gasket 18' intervening. Said topwall has anupstanding peripheral flange 19 within which the flange 17 is centered.The lower body member 14 is chambered, having a rectangular sidewall 20extending upwardly from the inner circumference of the annular flange17, said sidewall merging into an upper wall which extends inwardly atthe level of said axial plane, forming a flat face 21. Said lower bodymember is formed with a reentrant rectangular recess, the bottom wall 22of which has upturned marginal portions which merge integrally with theinner edge of said flat face. The reentrant recess constitutes thetrough of the mixing receptacle.

The lower body member 14 is secured to the top wall 10 of the pedestalby studs 23 which passthrough registering holes in the top wall 10 andin the base flange 17. The chamber 24 defined between the top wall Itand the wall structure of the lower body member 14 is for the receptionor circulation of a coolant or heating medium for controlling thetemperature of the batch. The temperature control medium is carried toand from the chamber 24 by hoses, not shown, which connect to inlet anddischarge nipples 25, emanating from the sidewall 9 of the pedestal atopposite sides and being connected Figure 5 is a vertical section of aslightly modified form the invention. This unitwhich is in effect apower plant includes a base 2 upon" which is mounted the mixer 33,

to conduits within said pedestal which have elbowed ends 26, the latterbeing connected to the top wall it at opposite sides. The nipples arepreferably of the selfclosing type so that the temperature controlmedium can be retained, when the hoses are disconnected to enable themixer to be moved away from the base 2 for pouring out the batch.

The upper body member 15 which is in effect an upper extension of thetrough of themixing receptacle, com- .prises a surrounding sidewall 27of rectangular crosssection, having an outwardly extending flange 28 atthe bottom, the under face 29 of which is coextensive with the matingface 21 of the lower body member. These faces are precisely machined andcome together to form a joint without the use of a gasket. At oppositesides of the mixing receptacle the faces 21 and 29 of the respectivebody members are indented to form pairs of semi-cylindrical recesses,which together form the bearing seats previously referred to. The upperbody member is kept in place by oppositely disposed quickly detachablelatches 30, hingedly secured to the sidewall of the lower body memberand each having a retractable keeper 31 adapted to grip the flange 28 ofthe upper body member, with stifily yielding means for retracting it.The latches are not part of the present invention and need not be morespecifically described. A rigid cover 32 is provided for the mixingreceptacle, which rests freely upon the upper edge of the upper bodymember, and has an internal flange 33 for holding it in place. Saidcover is unattached and freely removable.

The mixing receptacle is furnished with a pair of cooperating rotarymixing blades 34, commonly known as Z-blades, from the appearance oftheir mixing portions, viewed in elevation. Each ofthese blades isprovided with circular end faces 35, in planes perpendicular to the axesof rotation of the blades, the latter having each a helically twistedportion 36 in between, and having integral journals 37 at their ends.Bearing bushings 38 are fitted upon the journals and have flanged innerends, the flanges of which fit in circumferential rabbets in the bodymembers which extend about the bearing apertures. The bushings areretained upon the journals by means of snap rings 39 which interlockwith grooves 40 in the outer portions of said journals so that theblades with bushings may be removed as a unit. The length of the bladesbetween said end faces is such that there is substantially no end playbetween the blades and bushings. The flanges and blade unit or means isprovided for inhibiting axial slippage of the bushings in the bearingapertures. Each blade at one end has the journal extended and providedwith an end slot 41 which cooperates, as will appear, with a tongueformed on the complementary coupling element of the gear assembly. Thebearing bushings 38 are snugly retained in their seats or hearingapertures 16 by the weight of the upper body member 15 and theadditional clamping pressure exerted by the latches 30, so that the snaprings play no part in holding the bushings in place while the mixingreceptacle is assembled, their sole function being to hold the bushingson the journals when the blades are freed from the assemblage. Saidbushings are made of a plastic characterized by its resistance to wearand high temperatures, its non-abrasive behavior toward the journals, byits non-wettability by most liquids. The utility of this last mentionedproperty will be referred to in due course. Specifically, a plastic isemployed having a tradename Teflon, the chemical nomenclature beingpolytetrafiuoroethylene, which has the aboveproperties in a satisfactorydegree.

The versatility of the laboratory mixer is enhanced by the provision ofmeans for maintaining, when desired, an ambient vacuum about the mixingreceptacle, which means may be readily installed within a moments time,without tools, or laid aside if not to be used.

In prior batch mixers vacuum has generally been drawn directly on themixing chamber itself. Among other disadvantages this arrangement hasthe objectionable feature of causing air to be drawn into the batchthrough the bearings thereby defeating the exclusion of oxygen from themix, which exclusion in the case of certain mixtures, may be the veryobject of mixing them under vacuum. The entrainment of air during themixing may also, with batches of certain viscosity, convert the batchinto a froth or lather and impair the efficiency of the mixingoperation.

Packing glands are normally required to keep the mixing chamberair-tight if the vacuum were drawn directly therein. Such glands woulddeteriorate rapidly in contact with corrosive and solvent chemicalsseeping from the mixing chamber and would require frequent replace- 4meat. Packing glands, furthermore, cannot readily be disassembled forcleaning and reassembled.

Another drawback encountered in mixers of the type in which the air isevacuated directly from the mixing chamber, is that the batchnecessarily comes into contact with some of the surfaces which must besealed to maintain the vacuum. For example, the cover of the mixingchamber would have to make an air-tight fit with the top edge of themixing receptacle that it overlies. But the batch must be poured outover this very edge. If the batch were corrosive, deterioration wouldeventually beset the sealing surface and the joint could no longer bemaintained air tight.

The present invention, on the contrary, does not employ means forimposing the vacuum directly upon the mixing receptacle, but surroundsit with a plenum in which sub-atmospheric pressure may be maintained.Since there is no pretense of sealing the mixing chamber from saidplenum, there will be a balanced subatmospheric pressure both within andwithout the mixing chamber. For establishing this plenum, the mixer 3includes a cylindrical shell 42 which surrounds the mixing receptacle inspaced relation thereto, functioning as a jacket, and has its lower endfitted into an external rabbet extending peripherally about the upperend of the pedestal 7. The upright wall of said rabbet has acircumferential groove in which an O-ring 44 or equivalent packing ismounted, which presses against the shell forming a seal. The upper endof the shell is closed by a cover 45, also formed with a'peripheralrabbet 46, at its outer end, forming a shoulder 47 which rests upon theupper end of the shell, and a circumferential flange 48 that slidablyfits within said shell, said flange having a surrounding groovecontaining an O-ring 49 which provides a seal between said shell andcover. The cover is provided with a nipple 50 for the attachment of thehose of the evacuating means, and with a relief valve 51, which can beof any conventional structure.

Since the cover 32 is a loose fit upon the mixing chamber and neithersecured nor sealed, it follows that the air will be equally depletedboth within and without the mixing chamber when a vacuum is drawn sothat the possibility of air being drawin into the batch is eliminated.It also becomes immaterial whether the surfaces of the mixing chamberover which a corrosive batch might be poured, become rough or otherwisemarred, for such surfaces are not relied upon for a sealing function.

It will be noted that in the present invention the motor and gear boxhave been excluded from the chamber of the plenum. Obviously the motorcould not be practically operated in a vacuum, due to need forventilation, also in some instances because of fire hazard. From thepractical standpoint, in order to obtain maximum con venience andmobility in assembling and disassembling the shell and cover componentsof the plenum chamber, these are made as small and as simple aspracticable, therefore, the gear box as well as the motor are excludedfrom the plenum. This necessitates the provision of sealing meansbetween the shell and gear box.

It will be noted in the drawings that the shell 42, on one side, at anintermediate position between its upper and lower ends, is provided witha flat depressed area 52, the outer surface of which is in a chordalplane with respect to the adjacent cylindrical surface of said shell.The shell in this area is provided with an opening 53 of such length andwidth as to amply surround the geometrical axial projections of theblade journals carrying the coupling elements, when the shell is in itsnormal which are axially aligned with said blades when the shell is inproper position. Said passages make a slip-joint connection withcomplementary extensions on the shaft housing 56 of the gear box 5.

Said gear box comprises a casing which houses 57 receiving powertransmitted from the motor througha shaft 58, entering the casing at oneend and having an oil seal 59. The worm meshes with a worm gear '60mounted upon a shaft 61, having a collar 62 which thrusts against abearing 63. A spur gear 64 is also carried by this shaft which mesheswith a spur gear 65 on a parallel lay shaft 66. The shafts 61 and 66 arecarried in suitable bearings, the forward bearings being seated in theshaft housing 56. In front of said forward bearings are the oil seals 67and 68 for the respective shafts. Like the shaft 61, the shaft 66 has acollar 70 thrusting against a bearing at its rear end. The shaft housing56 is bolted to the oblong cover plate 69 and the latter bolted tothe-body of the casing.

The shaft housing 56 is formed with the extensions 71 and 72 which makea sliding fit within the corresponding passages 55. Said extensions areformed with interior annular grooves 73 in which o-rings 74'are seated,sealing the joints between said extensions and the walls of saidpassages. The forward ends of the shafts 61 and 66 are formed withreduced outer ends, furnished with coupling elements each comprising acylindrical cap 75 with a deep cylindrical bore 76 into which thereduced end of the shaft slidably fits. The outer ends of said cap havetransverse tongues 77' adapted to interdigitate with the end slots 41 ofthe adjacent coupling elements of the blade journals. The caps 75 areslotted as shown at 78 and pins 79 project radially-from the reducedends of the shafts through said slots, by which means the caps andsprings 79a are retained and the extent of yield of the caps determined.v c

it is to be noted that in the embodiment of the invention selected forpurpose of illustration the gears 64 and 65 are of different diameter,therefore, the mixing blades will be driven at different speeds. Thismakes 'it essential that the pathsof rotation of the blades do notintersect in order to avoid collision of the blades. It is contemplated,however, that the gears 64 and 65 be freely splined to their. respectiveshafts so that by removing the forward end plate 69 together with theshaft housing 56, the gears may be freed'so that they may he slipped offand substituted by gears of equal size, imparting equal speed to theblades. With gears of equal diameter the type of blades shown maybeused, or substituted by other known types of blade, each of which in thecourse of its rotation may invade the cylinder of revolution of theother without colliding if the mixing receptacle is made sufficientlylarge to provide for mixing blades of larger overall diameter. Thus,various types of mixingare available to the subject apparatus, and byreversing the motor the direction of mixing can also be reversed so thatthematcrial of a batch can be Worked toward or away from the center ofthe mixing. receptacle, as desired. t 1

The gear boxincludes a foot portion 80 which is secured to the base 2 insuch a position that the axes of the shafts 6l'and 66 are parallel tothe tracks 6. Therefore, when the mixer is placed upon the tracks theaxes of the bladeswill be coaxial with said shafts. In order toorientate the shell 42 so that passages 55 also will be coaxial withsaid shafts an index may be provided in the form of a vertical scoremark 81, for example, on the outer surface of the shell and the adjacentside wall of the pedestal, intersecting the circumferential line ;ofjunction between said parts.

;taining the batch to be mixed. is placed upon the tracks,

the shell is slipped into place over the O-ring 44, and the assembly ispushed toward the. gear box as far as it will G go. Since thecoupling'tongues 77 will probably not be in the same phase ofdisplacement as the coupling slot 41, the coupling caps 75 will bedepressed. The clamp 82 will now be tightened to press the keeper 83against the flange 11 of the pedestal. The keeper is free on the shank84, the latter being threaded into an anchor pin 85 on the under side ofthe pedestal, bridging a slot through which the shank extends. The knob'86, fixed to the shank presses against the keeper. It is to be observedthat there is no component of the pressure of the keeper tending toforce the mixer toward the gear box. When the position of the mixer hasbeen fixed by the keeper, the motor is started, the coupling caps turninto the same displacement phase as the blade shafts so that the tonguesspring into the slots and the mixing proceeds. This feature, whichobviates the necessity for preliminary mating by hand of the blade andgear shaft coupling slot and tongue, is a great convenience. If vacuumis to be employed, the cover is then put on with the O-ring 49 bearingagainst the inside of the The shell can also be left off if no vacuum isto release the latches and lift off the upper body of disassociation topermit thorough cleaning. This is particularly important both as to thetime element and the ability to obtain thorough cleanliness in themixing sure upon the sealing instrumentalities.

of successful experimental batches of different substances,

without contamination.

While ordinarily there is no creeping or seeping of the batch oringredients thereof, through the hearings or through the joint betweenthe upper and lower body members, there are conditions under which suchseepage may take place, as for example, when the batch includes a fluentvolatile solvent, or one of low density, in which case theloss of anappreciable amount of solvent may interfere with the proper mixing ormaterially alter the constituency of the batch.

Figures 5, 6 and 7 show a modified form of the invention in which anovel sealing system is interposed between the upper and lower bodymembers and between said body members and the journals of the blades forpositively preventing seepage at those points where it might occur. Itisto be understood that the end positionv between body members of suchpositive sealing means suggests that the upper body member be bolted tothe lower body member rather than securedmerely by yielding latches, inorder to obtain 'the requisite presvSaid figures show only those membersof the mixer as previously described, which it has been considerednecessary to alter in order to incorporate the-said sealing system, itbeing understood that these members can be substituted for theircounterparts in the-originally described structure.

.-Therefore, only those parts which have been modified will now bedescribed.

Referring first to the blade unit 87, the outer faces 88 of the bladesare provided with annular channels 89 forming seats for quad-rings 90,these being rings of' rubber or like material, a rectangularcross-section, having medial grooves extending circumferentially aboutall four faces", affording displacement spaces. The rings are .somewhatlarger than the channels in which they are squeezed, the ensuingdistortion displacing some of the mass of said rings into said spacescausing a reaction pressure of they ring against the sides of thechannel and the adjacent face of the Teflon washer 91; The circularbearing aperture 92 formed between the upper and lower body members 94and 93 are each provided on the sides adjacent to faces 88 of the bladewith the circumferential rabbet 95 forming a seat for the said Teflonwasher. At the outer side of the Teflon washer the journals of the bladeare furnished with cylindrical bearing bushings 96, preferably made ofnylon or its equivalent, being inflexible. Said bushings are formed eachwith a circumferential channel 97 in its inner end wall and a similarchannel 98, circumferentially about its exterior cylindrical wall.Quad-rings 99 and 100 are seated in said channels, the one to press theTeflon washer on the side opposite the quad-ring 90 and the other topress the walls of the lower halves of the bearing aperture 92 and alsothat part of an extensive molded gasket 101 which is exposed at the faceof said bearing aperture through a slot communicating with a chamber inwhich said gasket is confined and which will now be described.

This leads to a description of the modified upper body member 94, thelower part of which has an outward extension about all sides. Saidextension is formed with a deep recess 103 continuing uninterruptedlyabout said extension, opening in the lower face of said upper bodymember and intersecting the semi-circular walls of said bearingapertures carried by said upper body member. Said recess extendsdepthwise to a level above the apices of the upper arcs of said bearingapertures, as indicated by the numeral 104. The intersection of saidrecess with the walls of the bearings apertures forms slots abovereferred to through which the gasket 101 is exposed.

'Said gasket, per se is illustrated in Figure 7 and is rectangular inshape, having a general depth just a little greater than the depth ofthe recess 103 so that when it is snugly seated in said recess itprojects slightly beyond the under face of the upper body member. Saidgasket is formed on opposite sides with semi-circular indents 105 ofslightly smaller diameter than the bearing apertures so that it extendsslightly beyond walls of the bearing apertures. Said gasket ispreferably made of a rubber-like material such as neoprene.

The upper body member is formed at opposite sides of the outwardextension with integral lugs between the bearing apertures to receivestuds for securing the body members together with the gasket 101 pressedinto sealing contact with the contiguous face of the lower body memberand with the upper half of the quad-ring 100, and pressing saidquad-ring into sealing contact with the lower half of the bearingaperture. In order to minimize the number of studs, in the interest ofease and quickness of assembly, the upper body member is provided on theunbolted sides with upstanding ledges 106 permitting the supplementaryemployment of latches such as those hereinbefore described, or in theevent that the substances to be mixed are non-seepable, the studs may beleft out and sole reliance placed on the latches.

Referring to that part ofthe sealing system which afiects the bearings,the bearing bushings 96 are held on the journals by'snap rings 39 seatedin grooves 40. Since the blades will be pushed back manually in order toexpose the grooves 40 for the insertion of the snap rings, there will beonly light frictional pressure transmitted through the bushings andTeflon" washers to the quad-ring 90 so that the rotary movement will berestricted to the quad-ring 90 against the Teflon washer, and thesnap-ring against the outer end of the bearing bushing, allother partsof the sealing system remaining fixed. The Teflon washer beingnon-wettable by most substances acts as a normal barrier againstseepage, the quad-ring 100 forming a positive circumferential stopagainst leakage along the exterior face of the bearing bushing, whilethe quad-rings and 99 supplement the natural seepage repellent propertyof the Teflon washer in positively sealing the leakage path about saidwasher.

Referring nowto the modified lower body member 93, this is formed atopposite sides with the integral ribs 107, providing suflicientthickness of material to coat the threaded bores 108 for the studs 109,and also being for purpose of reinforcement. Said lower body member isalso cast with reinforcement ribs 110 on the interior of the alternatepair of opposite sides.

It will be understood that by the removal of the studs, the upper bodymember 94 may be lifted off, together with the molded gasket 101,thereby releasing the blade unit, including the bearing bushings, theTeflonv washers and the quad-rings. These may be separately disassembledafter removing the snap rings. It is thus apparent that the mixer withthe modified components may be disassembled and reassembled withpractically the same facility as the originally described mixer.

It is to be understood by those skilled in the art that the arrangementof parts and the specific details of construction are by way of exampleand not to be construed as necessarily limiting the scope of the pendingclaims.

We claim:

1. Mixing apparatus comprising a mixing receptacle including lower andupper body members, each being formed on opposite sides withthe'matching halves of coaxial cylindrical bearing apertures, said bodymembers being separable in a horizontal plane embracing the axis of saidbearing apertures, a blade unit comprising a blade having end facesperpendicular to its axis of rotation, and having coaxial journalsextending outwardly from its end faces, bearing bushings mounted uponsaid journals, fitting said apertures, said journals projecting slightlybeyond the outer ends of said apertures, said bushings having flangedinner ends fitting in circumferential rabbets in said body memberssurrounding said apertures, means for inhibiting axial slippage of saidbushings in said apertures, in the assembled apparatus, releasable meansco-acting with the projecting portions of said journals for retainingsaid bushings upon said journals when said blade unit is freed from saidbody members, and means for clamping said body members together.

2. Mixing apparatus as claimed in claim 1, said bushings being made ofpolytetrafluoroethylene, a plastic characterized by being non-wettableby most substances, whereby with respect to the mixing of suchsubstances. seepage through the joints of said bushings with saidjournals and bearing apertures, is suppressed.

3. Mixing apparatus comprising a mixing receptacle including lower andupper body members, each formed on opposite sides with the matchinghalves of a pair of coaxial cylindrical bearing apertures, said bodymembers being separable in a horizontal plane embracing the axes of saidbearing apertures, cooperating blade units, each comprising a mixingblade having end faces perpendicular to its axis of rotation, and havingcoaxial journals. extending outwardly from said end faces, bearingbushings mounted upon said journals fitting said bearing apertures, saidjournals projecting slightly beyond the outer ends of said apertures,said bushings having flanged inner ends, the flanges of which fit incircumferential rabbets in the body member surrounding said apertures,means for inhibiting axial slippage of said bushings in said apertures,in the assembled apparatus, the projecting portions of said journalsbeing grooved circumferentially, and snap rings removably seated in saidgrooves, for retaining said bushings upon said journals so that saidblade with bushings may be removed as a unit, and means for clampingsaid body members together.

4. Mixing apparatus comprising a mixing receptacle including lower and'upper body ut-embers, each formed on opposite sides with the matchinghalves of coaxial circular bearing apertures, mixing blades 'journaledin about the upper end of said recess, constituting a surface of thejoint between said body members, said lower body member below said planebeing formed with a side wall integral with said planiform face,surrounding the dished portion of said lower body member in spacedrelation thereto and extending below it, forming a chamber, and meansfor admitting a heating medium to said chamber beneath said reentrantportion being chambered and fitted for circulation of a heat exchangingmedium, said chamber being extended to surround the sides of saidreentrant recess. I

5. Mixing apparatus comprising a base having a circumferential rabbetthereabout defining a horizontal supporting shoulder and a cylindricalface, said face being formed with circumferential groove, a mixingreceptacle comprising a lower and an upper body member, each beingformed at opposite sideswith the matching halves of coaxial circularbearing apertures, said body members being separable in a horizontalplane embracing the axes "of'said bearing apertures, a driven blade unit"within said mixing receptacle having end journals, bearing bushingsremovably retained upon said journals and seated in said bearingapertures, means for clamping said body members in sealing relation withone another and with said bearing bushings, a jacket including a shellabout said mixing bered to form a heating chamber, and a heating mediumconduit communicating with said chamber.

7. Mixing apparatus comprising a hollow pedestal having a planiform"face at the top, and being provided with a circumferential rabbet aboutthe top defining a horizontal supporting shoulder and a circumferentialwall upstanding therefrom, a mixing receptacle mounted on said pedestalin secured relation thereto, comprising upper and lower body membersresting one upon the other, each formed on opposite sides with thematching halves of bearing apertures, said lower body member having atransverse wall dished between said bearing apertures to form the lowerpart of the chamber of said mixing receptacle, said lower body memberbeing hollow below said wall defining a chamber for a heat exchangingmedium, conduits extending through said pedestal below the level of saidrabbet and communicating with said heat exchanging medium chamber, ablade unit including a blade with journals and bearings on said journalsseated in said bearing apertures retained by the interengagement of saidbody members and freed for removal by their separation, a tubular shellsurrounding said mixing receptacle having its lower end slidablytelescoped over theupstanding wall of said rabbet, forming a slip-joint,one of the joint-forming faces being grooved, and an O-ring seated insaid groove, a removable cover for said shell having a peripheralshoulder adapted to rest on said shell, and a depending flange adaptedto telescope relative to said shell and make a slip-joint therewith, oneof the slipjoint faces being grooved and an O-ring seated in saidgroove, said cover being provided with fittings adapting it to beconnected to vacuum drawing apparatus.

8. Mixing apparatus comprising a base, a mixing reg ea ness lower bodymembers each formed on opposite sides with the matching halves ofbearing apertures, bearing bushings within said apertures and a bladeunit within said :mixing receptacle journaled in said bearing bushings,the adjacent faces of said body members making a-butt joint with oneanother and with said bearing bushings, means for securing said bodymembers together, a shell adapted to he slipped over said'mixingreceptacle with its lower end lapped over the upper end of said base,forming a joint, sealing means between the lapped portions of saidjoint, a cover for said shell forming therewith an enclosure for saidmixing receptacle, said cover having a flange in lapped relation to theupper end of said shell, forming therewith a slip-joint, and sealingmeans between the faces of said joint, said cover being provided withfittings adapting it to be connected wit a vacuum pump, and to relievethe vacuum.

9. Mixing apparatus as claimed in claim 8,'the upper body member havinga peripheral slot extending all around and of such depth as to extendabove the upper arcs of the bearing apertures, and a molded gasket offlexible, elastically deformable material shaped to iill said slot, toconform to theshape of the joint surface of saidupper body member and toextend slightly outward with respect to said surface, and means forclamping said upper and lower body members together to press said gasketin sealing relation to the entire joint interface. 10. Mixing apparatuscomprising a mixing receptacle including upper and lower body memberseach formed on opposite sides with the matching halves of bearingapertures, said body members being separable in ahorizon'tal planeembracing the axes of said apertures, bearing bushings within saidapertures, and a blade unit within said mixing receptacle 'journaled insaid bushings, the adjacent faces of said body members making a buttjoint with'e'ach other and with said bearing bushings, the 'upper bodymember having a peripheral slot extending "clamping said upper and lowerbody members together to press said gasket in sealing relation to theentire joint interface, including the contiguous arcs of said bushings.

11. In combination, a mixer including a mixer receptacle, a mixing bladetherein journaled on a horizontal axis, a shaft extending horizontallytherefrom having a coupling element at its end, a gear assembly fordriving said blade, said gear assembly including a shaft having acomplementary coupling element at its adjacent end, one of said couplingelements being yieldable, means for a common support for said gearassembly and mixer, a casing for said gear assembly secured to saidsupport, linear guided means secured to said support parallel to saidshaft of the gear assembly, slide means at the bottom of said mixerparallel to the blade shaft, said mixer being adapted to be guidedlymoved upon said support to bring said coupling elements into yieldinginterengagement, a shell adapted to be placed in enveloping relation tosaid mixing receptacle, means between the lower end of said shell andthe adjacent part of said mixer for forming a sealed circumferentialjoint about said mixer, a fitting secured to a side of said shell havinga cylindrical opening communicating with the interior of said shell andextending outwardly therefrom, said shell being freely circumferentiallyadjustable to bring said opening into axial alignment with the bladeshaft, and an extension project ing from the casing of said gearassembly surrounding the coupling element of the shaft of said gearassembly adapted to interdigitate with the. opening through said fittingwhen said mixer is approached to said gear assembly 'sufiicient todepress said yieldable couplings, an Q- ring seated in a circumferentialgroove in one of the adjacent faces of said interdigitated members, acover for said shell having a circumferential flange in lapped relationto the upper end of said shell and an O-ring seated in a circumferentialgroove in one of the adjacent lapped faces, and a coupling connectioncarried by said cover communicating with the space between said shelland receptacle, adapted for connection to vacuum drawing apparatus.

12 Mixing apparatus including a mixing receptacle, a mixing bladejournaled therein on a horizontal axis, a shaft extending horizontallytherefromhaving a coupling element at its end, a gear assembly fordriving said blade including a shaft for a complementary couplingelement, one of said coupling elements being yieldable, a casingincluding a shell and cover removably and sealingly enveloping saidmixing receptacle, a fitting on said shell at one side thereof having apassage therethrough coaxially with said blade shaft, a casing aboutsaid gear assembly including a hollow extension surrounding said gearassembly shaft, throughwhich said gear assembly shaft extends with saidcomplementary coupling element proing two blades journaled in said mixeron parallel shafts,

each having a coupling element, and two parallel gear assembly shaftshaving coupling elements complementary to the respective blade shaftcoupling elements,-the fitting on said shell having passagestherethrough coaxial with the respective blade shafts, the gear assemblycasing having an extension for each passage forming a sealed slip-jointwith the walls thereof, and separate gears for driving said gearassembly shafts, said gears being freely removable for replacement byother gears, for adjusting speed ratio of said blades.

14. Mixing apparatus comprising a base having a circumferential rabbetthereabout, defining a horizontal supporting shoulder and a cylindricalface, a mixing receptacle seated on said base comprising upper and lowerbody members separable in a horizontal plane, and a driven blade unitjournalled in said receptacle on'an'axis in said plane of separation,and retained through the normal juxtaposition of said members, means forsecuring said body members together, removable jacket means envelopingsaid mixing receptacle in airtight manner including a shell seated insaid rabbet in sealed relation to said cylindrical face, and couplingmeans for connection to vacuum drawing apparatus carried by said jacketmeans;

15. In combination, mixing apparatus as claimed in claim 14, and adriving unit therefor, said blade unit being formed with a couplingelement at one end, said driving unit being provided with acomplementary coupling element, said shell having an opening in one sidegiving coupling access to said coupling elements, and interengagingsealing means between said driving unit and shell, about said opening.

16. Mixing apparatus comprising a base, a mixing receptacle mounted onsaid base comprising upper and lower body members, each formed onopposite sides, with the matching halves of bearing seats, bearingbushings within said seats and a blade unit within said receptaclejournalled in said bushings, the adjacent faces of said body membersmaking a butt joint with one another and with said bushings, meanssecuring said body members together, jacket means enveloping saidreceptacle in airtight manner, including a shell lapped over the upperend of said base forming a sealed slip joint, said jacket means beingprovided with fittings adapting it to be connected with a vacuum pump,and to relieve the vacuum.

References Cited in the file of this patent UNITED STATES PATENTS615,683 Day Dec. 13, 1898 1,490,617 McKillican Apr. 15, 1924 1,584,562Kulenkampfi May 11, 1926 2,017,116 Bonell Oct. 15, 1935 2,376,593 HellenMay 22, 1945 2,411,006 Sharp Nov. 12, 1946 2,552,166 Gardiner May 8,1951 2,702,730 Ivanofi et a1 Feb. 22, 1955 FOREIGN PATENTS 1,030,617France Mar. 18, 1953

